As a muscle memory check from things 33 years ago, I wanted to know how much the #ibm #mainframe under #zOS has changed from /370 back then.

Yes, we are now at #JES3 - and the new things for me were PDSEs and USS - feels weird calling #OMVS and having a #Linux environment #shell on the mainframe. Ah yes, we did not have #FICON either back then to define CHPIDs but the 3380 and 3390 were actually huge boxes connected via #bus and #tag cables.